Stock Plans (Fair Value of "Look Back" Option for ESPP Weighted-Average Assumptions) (Details) (Employee Stock Purchase Plan [Member], USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Stock Purchase Plan [Member]
Schedule of stock options and employee stock purchase plan weighted-average assumptions
Expected dividends	0.00%	0.00%	0.00%
Stock price on valuation date	$ 11.96	$ 17.54	$ 14.03
Expected volatility range	71.00%	41.00%	54.00%
Risk-free interest rate	0.10%	0.15%	0.21%
Expected life (in years)	6 months	6 months	6 months
Fair value per share	$ 4.16	$ 4.73	$ 4.78

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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